Diabetes mellitus is a chronic metabolic disorder of multiple aetiology, characterized by chronic hyperglycemia with disturbance of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action, or both. The effect of diabetes mellitus includes long-term damage, dysfunction and failure of various organs. Diabetes mellitus is usually divided into two major categories:                Type 1 diabetes (formerly insulin-dependent diabetes mellitus) encompasses the majority of cases which are primarily due to pancreatic islet beta cell destruction, usually develop in childhood or adolescence and are prone to ketosis and acidosis. Type 1 diabetes accounts for around 10% of all diabetes.        Type 2 diabetes (formerly non insulin-dependent diabetes mellitus) includes the common major form of diabetes which results from defect(s) in insulin secretion, almost always with a major contribution from insulin resistance. Type 2 diabetes accounts for around 90% of all diabetes.        
The onset of symptoms in type 1 diabetes is usually acute and frequently follows an antecedent viral infection which might be the trigger to a process leading to destruction of beta cells secondary to auto immune insulitis. When beta cells destruction reaches the critical point, the patient's reduced insulin levels lead to hyperglycaemia with the typical symptomatology of type 1 diabetes.
Type 1 diabetes can affect many major organs, including heart, blood vessels, nerves, eyes and kidneys leading to cardiovascular diseases, retinopathy (up to blindness), neuropathy and nephropathy (up to dialysis). Adequate control of blood glucose concentration can dramatically reduce the risk of many complications. The main treatment regimen for type 1 diabetes involves administration of insulin, usually subcutaneously. There are different regimens for insulin therapy, and various combinations of long acting, intermediate and short acting insulins can be used depending on the context. Continuous insulin delivery using a pump can also be used to accurately control blood glucose concentration. The more intensive regimens tend to provide better control of blood glucose, however they are much more intrusive to the patient's life, which can be a particular problem when treating juveniles with this condition.